Riello 40 G5X won't start

[MrDuck]

This burner has started locking out when it should be starting up. If I move the fan on a fraction it will start (after pressing the lockout button) and then runs normally. But once the motor has stopped it will not then restart without my repeating the manual fan movement.

I have taken the air cowl off and tried turning the fan by hand. It mostly turns freely but has a spot on each revolution at which it goes quite stiff. I think that when the motor stops it is at this stiff point, from which it then won't restart.

Please can some kind person suggest a solution. This unit is quite old but has functioned very reliably for the last few years.

 

[Boilerman2]

You will need to separate the oil pump from the motor to see which component has the tight spot, this is the part that will need changing

Obviously if changing the oil pump a boiler engineer will be needed to ensure the oil pressure is set on the new pump (critical adjustment!)

how tight does the motor/pump go? if only slightly tight it might be worth changing the Capacitor first as if this is weak, the slightest resistance would stall the motor - the capacitor is a cheap and easy part to replace

 

[MrDuck]

That makes sense. The resistance is not huge - it's like starting a very small single cylinder engine when the compression increases the resistance, and then eases off after TDC. But I can understand why it stops the motor starting. I changed the capacitor three years ago when I had a starting problem when the motor was cold, but on that occasion after starting once it always restarted again. Now it locks out on every restart unless I manually push it past the high spot. Can the capacitor have degraded so fast?

I have bought a replacement coupling in anticipation of separating the motor from the pump. Are there any tricks to make this dismantling easy? I can see that I could end up removing pipes and fastenings unecessarily.

Finally, how stiff should the oil pump be? Should it turn smoothly with a no more than a thumb/finger twist on the shaft or is it normally 'lumpy'?

 

[MrDuck]

Well I replaced the motor start capacitor today with immediate improvement. I will arrange for the old component to be measured. I am inclined to think that the problem is a combination of a partially degraded capacitor and a sticking motor/pump so I plan to separate the oil pump as suggested and fix the cause of the sticking.

I also plan to find out more about capacitor lifetime - three years light usage doesn't seem a lot to me (I'm an electronics engineer by profession). Maybe I need a special quality component ( I'm currently using Ducati, which is a well known make).

 

[Boilerman2]

Turn off the oil.
Disconnect the feed to the nozzle (12mm spanner)
Disconnect the thin pipe to the hydralic jack if fitted (8mm spanner)
loosen three M4 Allen screws around the pump mounting hub
The pump can now be pulled away - you will need to twist it clockwise to release the nozzle pipe -CAREFULLY!!

No need to undo the flexible oil supply pipe/s

The oil pump shaft should turn by hand smoothly with no notchiness

 

[Agile]

I also plan to find out more about capacitor lifetime - three years light usage doesn't seem a lot to me (I'm an electronics engineer by profession). Maybe I need a special quality component ( I'm currently using Ducati, which is a well known make).

As an electronics engineer I would have thought that you would have have measured the capacitance before changing it.

I looked at an old 2.6 μF pump cap I have here and its interesting the lifetime shown on it against various voltages. 30,000 hours @ 400 vac but only 3000 hours at 500 vac. That latter is just a few months!

Perhaps you need to measure the applied voltage?

Because of the difficulty of obtaining some models of replacement pumps for boilers I often check and where required just change the cap to repair the boiler. Saves the customer a lot of money.

Tony

 

[Boilerman2]

Erh? We're talking OIL PUMPS here Tony!!

 

[Burnerman]

Those Inter burners with the capacitor integral with the motor are a bit of a pain......I don't test the cap, just bung a spare on. If possible I like to hold the motor in the vice, and grip the shaft when turning it on (carefully)! to see if the starting torque is good.
John

 

[MrDuck]

I followed your very helpful instructions this morning and I believe I have fixed it. Not too easy to do as one of my flex lines made removing and refitting the pump difficult but I got there.

The cause of the sticking seems to have been a build up of rust both inside and outside the nylon coupling between the motor and the pump which prevented the coupling from compensating for misalignment. I have replaced the coupling with a new part but put a smear of grease on it first to stop future rusting. The motor now works as smooth as silk! This is a photo I took of the old coupling in case anyone is interested View media item 39785
Ideally I would have measured the motor run capacitor before replacing it but my home multimeter doesn't do capacitance. What I can say is that fitting a new capacitor transformed starting so when I do get round to measuring the old part I expect to find substantial loss of capacitance. I spoke to Riello about the need for regular capacitor replacement but got a very vague response (only when it's on the way out seemed to be the answer). I don't want to have to worry about my boiler not working in cold weather if I am away so a two yearly replacement may be appropriate. What do others think?

My grateful thanks for all the advice I have been given. I also found this YouTube video very helpful http://www.youtube.com/watch?v=_LcFqU2DBH8&feature=related as its shows what to expect when the components are dismantled.

 

[Burnerman]

Thanks for the update - I'm sure the fault was the capacitor all along!
John

 

[Agile]

Erh? We're talking OIL PUMPS here Tony!!

Yes, I did realise that!

But the electric motor operates on the same principle as circulator motors.

I do have to say I was surprised by the short life the manufacturer had stated on the cap!

Tony

 

[MrDuck]

I have done bit of research on the lifetime of motor run capacitors, results as follows:

1. In use the capacitor sees between 1.5 and 2 times the motor voltage (i.e. could be up to 480v in the UK).

2. The capacitor lifetime is VERY dependent on how stressed it is, so it's important to choose a component with as high a rated voltage as possible so it will be low stressed in actual use.

3. Typically motor run capacitors are triple rated with one voltage specified for a 30,000 hours life time, one for a 10,000 hour lifetime and one for 3,000 hours only.

4. The official Riello component is rated at 475 volts for a 10,000 hour life, whereas my Ducati capacitor is only rated at 425v for 10,000 hours, and some are only 400v rated. Indeed the genuine component is the highest rated I can find (i.e. the best). This explains why my Ducati capacitor has only lasted three years as it being stressed much more than a Riello part would have been. The 2.6uF capacitor referred to above would potentially have an even shorter lifetime.

The bottom line is that I have now ordered a genuine Riello spare (all be it at twice the price) and look forward to a much longer lifetime.

 

[MrDuck]

I have now been able to measure the capacitance of the Ducati motor run capacitor I recently replaced, and which would intermittently not start the burner motor.

It had gone down from a nominal 4.0uF (+/-5%) to 3.7uF. Now that's not a big reduction, and only 0.1uF below the allowed tolerance of +/-5% for a brand new component. So I am now inclined to think that it was the stiction due to the corroded motor/pump coupling that was the main culprit here. Something I need to watch out for in the future.

I also measured the original Riello motor run capacitor (new in 1993?) which had gone down to 3.5uF, and was replaced three years ago to cure the same type of starting problem. Looks like Riello original parts last better, as suspected.

Hope this is useful to someone!